Octane number is a measure of the effectiveness of power production. It is a kinetic parameter, therefore difficult to predict. Oil companies compiled volumes of experimental octane data (for most hydrocarbons) for the Department of Defense in the 1950's. For example, 2,2,4-trimethyl pentane (isooctane) has a defined octane number of 100, and n-heptane has a defined octane number of 0, based on experimental tests. Octane numbers are linearly interpolated and are generally hard to extrapolate, hence some predictions for mixes can be made only once pure sample values are determined.
Automobile gasoline is placarded at the pump as the average of research and motor octane numbers. These average octane numbers correlate to running a laboratory test engine (CFR) under less severe and more severe conditions, respectively, and calculating the average octane exhibited under these conditions. True octane numbers lie between the research and motor octane values. Aviation fuel has a “hard” requirement of 100 motor octane number (MON); ethanol has a MON of 96, which makes its use viable only when mixed with other higher octane components that are capable of increasing the MON to at least 100. Conventional 100 octane low lead (100 LL) contains about 3 ml of tetraethyl lead per gallon.
The inherent energy contained within gasoline is directly related to mileage, not to octane number. Automobile gasoline has no energy specification, hence no mileage specification. In contrast, aviation fuels, a common example being 100 LL, have an energy content specification. This translates to aircraft range and to specific fuel consumption. In the octane examples above, i-octane and n-heptane had values of 100 and 0, respectively. From an energy perspective, they contain heat of combustion values of 7.84 and 7.86 kcal/ml, respectively, which is the reverse of what would be expected based on power developed. Aircraft cannot compromise range due to the sensitivity of their missions. For this reason, energy content is equally important as MON values.
The current production volume of 100 LL is approximately 850,000 gallons per day. 100 LL has been designated by the Environmental Protection Agency (EPA) as the last fuel in the United States to contain tetraethyl lead. This exemption will likely come to an end in the future. In the United States, the Federal Aviation Administration (FAA) is responsible for setting the technical standards for aviation fuels. Currently, the FAA uses ASTM D910 as one of the important standards for aviation fuel. In particular, this standard defines 100 LL aviation gasoline. Thus any replacement 100 LL will likely also need to meet ASTM D910.
Although a number of chemical compounds have been found to satisfy the motor octane number for 100 octane aviation fuel, they fail to meet a number of other technical requirements for aviation fuel. This is true, for example, for isopentane, 90 MON, and sym-trimethyl benzene 136 MON. Pure isopentane fails to qualify as an aviation fuel because it does not pass the ASTM specification D909 for supercharge octane number, ASTM specification D2700 for motor octane number, and ASTM specification D5191 for vapor pressure. Pure sym-trimethyl benzene (mesitylene) also fails to qualify as an aviation fuel because it does not pass ASTM specification D2386 for freeze point, ASTM specification D5191 for vapor pressure, and ASTM specification D86 for the 10% distillation point. Table 3 herein shows these test results and the ASTM standard for both isopentane and sym-trimethyl benzene.
A number of methods are known for making mesitylene from acetone and include, for example:
liquid phase condensation of acetone in the presence of strong acids, e.g. sulfuric acid and phosphoric acid, as described in U.S. Pat. No. 3,267,165 (1966);
vapor phase condensation of acetone in the presence of a tantalum containing catalysts, as described in U.S. Pat. No. 2,917,561 (1959);
vapor phase condensation of acetone in the presence of a catalyst employing phosphates of the metals of group IV of the periodic system of elements, e.g. titanium, zirconium, hafnium and tin as described in U.S. Pat. No. 3,946,079 (1976);
vapor phase reaction of acetone in the presence of molecular hydrogen and a catalyst selected from alumina containing chromia and boria as described in U.S. Pat. No. 3,201,485 (1965);
vapor phase reaction of acetone using catalysts containing molybdenum as described in U.S. Pat. No. 3,301,912 (1967) or tungsten as described in U.S. Pat. No. 2,425,096; a vapor phase reaction of acetone over a niobium supported catalyst with high selectivity. The catalyst is preferably made by impregnating a silica support with an ethanolic solution of NbCl.sub.5 or an aqueous solution of a niobium compound in order to deposit 2% Nb by weight and by calcining the final solid at 550° C. for 18 hours at 300° C. The condensation of acetone produces mainly mesitylene (70% selectivity) at high conversion (60-80% wt) as described in U.S. Pat. No. 5,087,781.
It is known that alkynes can be cyclotrimerized over transition metal catalysts to form benzene derivatives (C. W. Bird in “Transition Metal Intermediates in Organic Synthesis”, New York, London: Academic Press, 1967, pp. 1-29) and U.S. Pat. No. 4,006,149). It is also known in the art to dimerize acetone to form isopentane. This process involves first dimerizing acetone to form diacetone alcohol which is then dehydrated to form mesitytl oxide. The mesityl oxide then undergoes gas phase reformation hydrogenation to form isopentane.
Although the prior art describes various methods in which acetone can be trimerized to form mesitylene in acid media, as well as various gas phase reactions in which acetone is trimerized in acidic heterogeneous catalytic surfaces such as silica gel, there still exists the problem of controlling the (1) extent of reaction (dimerization as opposed to trimerization) as well as (2) the selectivity of the reaction (minimization of unreacted side products) while maintaining (3) high throughput.
It is an object of the present invention to provide fuels for aircraft which replace 100 LL aviation gasoline. It is a further object of the present invention to provide high energy renewable fuels for use in turbines and other heat engines by the same methodology; the energy content and physical properties of the renewable components being tailored to the type of engine to be fueled.
It is another object of the present invention to provide a binary mixture of components which meet the technical specifications for aviation fuel of 100 LL octane. It is another object of the present invention to provide a non-petroleum based aviation fuel as a replacement of 100 octane which meets the technical specifications of the Federal Aviation Administration for 100 octane aviation fuels. Also disclosed is a process for the production of a biomass-derived fuel using bacteriological fermentation to produce the components of a binary chemical mixture which satisfies the technical specifications for 100 octane aviation fuel. It is yet another object of the present invention to provide a process for the production of a new chemical-based 100 octane aviation fuel from renewable sources.